Meaning
長芋 (ながいも, Naga-imo) is Chinese yam, a Japanese food (plants, tubers).
What is Chinese yam?
Nagaimo ( Dioscorea polystachya ) is a species of yam that is unique as the tubers can be eaten raw. In English, it is called "Chinese yam" or "cinnamon-vine", because the flowers are cinnamon-scented. Nagaimo is classified into ichō-imo (lit. "ginkgo-leaf yam" 銀杏芋), or yamato-imo (大和芋 ), depending on root shapes. In Japan, this species is sometimes mistakenly called the Japanese mountain yam ( yama-imo , 山芋). In Japanese cuisine, it is eaten raw and grated, after only a relatively minimal preparation: the whole tubers are briefly soaked in a vinegar-water solution, to neutralize irritant oxalate crystals found in their skin. The raw vegetable is starchy and bland, mucilaginous when grated, and may be eaten plain as a side dish, or added to noodles. The grated yam is known as tororo. It is used in the Japanese noodle dish tororo udon or soba and as a binding agent in the batter of okonomiyaki . In tororo udon and soba , the tororo is mixed with other ingrients that typically include tsuyu broth (often made from dashi), wasabi , and green onions.